Evidence Synthesis

What is Evidence synthesis?

Evidence Synthesis provides a broad and integrative approach to summarising and interpreting research evidence.
It can include various methods and is not limited to quantitative data.
It aims to offer a comprehensive understanding of a research topic by combining evidence from multiple sources and study designs.

Details

Evidence Synthesis

Evidence synthesis offers a broad and integrative approach to summarising and interpreting research evidence. It can include various methods and is not limited to quantitative data. It aims to offer a comprehensive understanding of a research topic by combining evidence from multiple sources and study designs.

Purpose:

To Integrate Research Findings: The primary aim is to combine and integrate findings from multiple studies to provide a comprehensive understanding of a particular research question or topic.
To Inform Decision-Making: To offer a consolidated view of the evidence that can inform practice, policy, or future research.
To Identify Patterns and Gaps: To identify patterns, trends, and gaps in the existing literature, helping to highlight areas where further research is needed.

Characteristics:

Broad Approach: Evidence synthesis can include various methods and approaches, including systematic reviews, scoping reviews, and narrative syntheses.
Comprehensive: It aims to encompass a wide range of evidence, including both qualitative and quantitative studies, to provide a holistic view of the research topic.
Qualitative and Quantitative Integration: May involve the integration of both qualitative and quantitative evidence, depending on the nature of the research question and the available studies.
Varied Methods: Utilises different methods to synthesise evidence, such as thematic analysis, narrative synthesis, or framework synthesis, based on the type of data and research questions.
Reporting: Results are typically presented in a summary form that may include tables, charts, and descriptive text to convey key findings and insights.

Timescale:

Varies Widely (2 to 12 months or more): The timescale for evidence synthesis depends on the method used and the breadth of the review.

Example

Example: The Global Burden of Disease Study

This large-scale synthesis of evidence integrates data from multiple sources to provide a comprehensive picture of global health, identifying key health challenges and informing policy decisions worldwide.

Title: Global Burden of Disease Study 2017

Published In: The Lancet, 2018

Purpose: The primary aim of the Global Burden of Disease (GBD) Study is to provide a comprehensive assessment of the health status of populations around the world. It quantifies the burden of diseases, injuries, and risk factors by age, sex, and geography over time.

Key Characteristics of the Review:

Comprehensive Scope: The GBD study covers a wide range of diseases, injuries, and risk factors across all countries. It synthesises data from numerous sources, including health surveys, administrative records, vital registration data, and epidemiological studies.
Systematic Data Collection: The study uses systematic methods to collect and harmonise data from various sources. This includes detailed and standardised protocols for data extraction, ensuring consistency and comparability across different data sets.
Quality Assessment: Rigorous methods are applied to assess the quality of data sources. This includes evaluating the completeness, accuracy, and consistency of data, and adjusting for biases and missing data where necessary.
Advanced Statistical Methods: The GBD study employs advanced statistical techniques, including meta-analysis and modelling, to estimate the burden of diseases and risk factors. This allows for the synthesis of data from diverse sources and the estimation of health metrics such as years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life years (DALYs).
Interactive Data Visualisation: The findings of the GBD study are presented through interactive data visualisations and detailed reports. This makes the complex data accessible to a wide audience, including policymakers, researchers, and the general public.

Key Findings:

The GBD study provides detailed estimates of the burden of various diseases and risk factors globally, regionally, and nationally.
It identifies leading causes of mortality and morbidity, such as ischemic heart disease, stroke, lower respiratory infections, and neonatal disorders.
The study highlights the impact of key risk factors, including smoking, high blood pressure, high blood sugar, and obesity, on global health.
It reveals trends over time, showing how the burden of diseases and risk factors has changed and identifying emerging health challenges.

Impact:

The GBD study has had a profound impact on global health research and policy. It provides crucial data for setting health priorities, allocating resources, and designing interventions to address the most pressing health challenges. Governments, international organizations, and researchers use the findings of the GBD study to inform health policies and strategies aimed at improving population health.

Summary:

The Global Burden of Disease study exemplifies the power of evidence synthesis to integrate data from multiple sources and provide a comprehensive assessment of global health. By systematically collecting, evaluating, and analysing vast amounts of data, the GBD study offers valuable insights into the burden of diseases and risk factors, guiding efforts to improve health outcomes worldwide. This large-scale evidence synthesis project demonstrates how combining diverse evidence can lead to a deeper understanding of complex health issues and inform effective health policies.

NIHR Example:

Recent Evidence synthesis (from NIHR Journals library database 30/7/2024)

Kingsbury SR, Smith LK, Czoski Murray CJ, Pinedo-Villanueva R, Judge A, West R, et al. Safety of disinvestment in mid- to late-term follow-up post primary hip and knee replacement: the UK SAFE evidence synthesis and recommendations. Health Soc Care Deliv Res 2022;10(16)

Funding: Health and Social Care Delivery Research (HSDR) Programme (Health and Social Care Delivery Research Volume: 10, Issue: 16, Published in June 2022) https://doi.org/10.3310/KODQ0769 https://www.journalslibrary.nihr.ac.uk/hsdr/KODQ0769/#/abstract

Video Resources

"Evidence Synthesis - What is it and why do we need it?" The video explains that evidence synthesis involves combining results from multiple studies to form a comprehensive understanding of a specific topic, which is crucial for informing healthcare decisions and policy-making. It is designed to be accessible to both professionals and the general public, making complex concepts understandable. This video is part of Cochrane's effort to increase awareness and understanding of evidence synthesis methods, particularly in the context of health and social care research. (Cochrane 3:29 minutes)